The present invention pertains to analog and digital data transmission and more particularly to remotely controlled switching between analog and digital data link transmission of a switching office.
In modern electronic telephone switching systems, large volumes of data are transmitted from one switching office to other switching offices. This data is supervisory and signaling data, related to the processing of telephone calls. In order to accomplish this data transfer, data links operated by modems are connected between switching offices. The data links provide for rapidly transmitting the supervisory and signaling data between these switching offices. This data is transmitted via the modems in an analog manner. Analog data is information which is conveyed by the amplitude or phase of a signal.
More recently, switching offices employ digital data transmission techniques via T1 carrier equipment. Digital data is concerned with discrete states of a signal, such as the presence or absence of a voltage. Digital data may be transmitted at higher speeds than analog. At the present time, the telephone system is approximately 50% analog and 50% digital transmission. It is expected by the year 1990, that the telephone system will be nearly 100% digital data transmission. Therefore, a considerable change in equipment from analog to digital has and will yet occur.
It is expensive for maintenance personnel to install new equipment and re-wire existing analog equipment for conversion to digital equipment. In addition, during testing of digital or analog transmission equipment, many changes from analog to digital and back to analog may be necessary. To electrically wire these changes by hand each time is time consuming, expensive and requires lengthy service interruptions.
In electronic switching offices, it is desirable to perform maintenance functions from a remote location since, it is expensive to have maintenance personnel located at each electronic switching office. Many switching offices may be monitored by a single electronic maintenance and assistance center. Therefore, it is desirable to provide remote changeover from analog to digital data transmission and vice versa from this maintenance center.
Accordingly, it is an object of the present invention to provide an economical and automated remote or local data link switching arrangement.